Rendering on CPU vs GPU how to enable CUDA and performance on older system
Your card is way too old, below the minimum specs needed for the current versions of blender.
From the manual
https://docs.blender.org/manual/en/latest/render/cycles/gpu_rendering.html

CUDA
CUDA requires graphics cards with compute capability 3.0 and higher. To make sure your GPU is supported, see the list of Nvidia graphics cards with the compute capabilities and supported graphics cards. CUDA GPU rendering is supported on Windows, macOS, and Linux.

Check the minimum requirements here too:
https://www.blender.org/download/requirements/
You can try using older versions (2.79 or below) which might work, but know that you might not get any benefits for using CUDA at all.
Also blender does not work with SLI.